Show the latest data index in the prompt

[Itaborala]

In many occasions, after using a vqhpreset file,referring to a Session Path, it is often the case that I need to sonify the same data over and over.
But it is hard to access the information on the latest index of the session folder after running map

Three solutions:

• Have the latest index show up in the VQH prompt: (index) VQH => (this might be confising, since this had a different purpose in other ICCMR projects (PaulisMIDI))
• Have a latest command to get this information printed out in the prompt
• Have an argument mapfile latest (Very nice, but also does not explicitly show the index, which might still be useful)